Dual probe tip signal acquisition probes, such as differential probes and single ended probes with a ground contact, are used in the electronic industry for measuring electrical signals from a device under test. The probing tips generally require variable spacing to connect with probing contacts having different pitch spacing. Early variable pitch probes off-set the probing tips from the probing tip axis so as to rotate the probing tips around the probing tip axis to vary the spacing of the probing tips. Probing tips of this type are describes in U.S. Pat. Nos. 6,400,167 B1, 6,404,215 B1, 6,603,297 and 6,828,768.B1 Generally, theses type of probing tips required a user to manually adjust each of the probing tips separately.
An improved dual probe tip signal acquisition probe system uses a thumb wheel attached to dual probing arms. A probing tip is attached to one end of each probing arm with the other ends of the probing arms secured to a pivot point. The thumb wheel is generally positioned midway between the pivot point and probing tips. The thumb wheel is attached to the probing arms in such a way that rotational movement of the thumb wheel in the clockwise or counter-clockwise direction causes the probing arms to rotate or pivot around the pivot point to vary the spacing between the probing tips. Examples of such probing tip systems are described in U.S. Pat. Nos. 6,276,956 B1, 6,967,473 B1, 7,212,018 B1 and 7,592,822 B1.
In the above dual probe signal acquisition probes, each probing tip scribes an arc as it is rotates about its pivot point. Another dual probing tip acquisition probe system laterally moves one or more probing tips to decrease or increase the spacing of the probing tips. U.S. Pat. No. 7,167,011 describes a variable spacing probing system having one or more probing tip displacement mechanisms disposed adjacent to one or both probing tips. The probing tips are formed at the end of semi-rigid coaxial cables with each semi-rigid coaxial cable secured in a retention block. One or both of the retention blocks are connected to an adjustment mechanism having a carrier receiving the retention block. The probe body into which the semi-rigid coaxial cables are mounted has at least one threaded aperture extending from the side of the probe body into which is secured a threaded cap screw. A user uses a hex-key wrench, screwdriver or the like to rotate the cap screw clockwise or counter-clockwise to decrease or increase the separation of the probing tips.
Another requirement for dual probe tip signal acquisition probes is probe tip compliance. Probing points on a circuit under test may not be at the same height. The probing tips should be able to compensate for these variations by axial movement of the probing tips. Compression springs, non-compressive set elastomer or the like have been used to provide axial movement of the probing tips. U.S. Pat. Nos. 6,828,768 B1, 7,102,370 B1, 7,167,011 B1 and 7,592,822 B1 describe various dual probing tip systems having probe tip compliance.
Dual probing tip signal acquisition probes should also provide lateral compliance as well as axial compliance. The most reliable connection to probing contacts on a device under test is when the probe is positioned normal to the probing contacts. However, this is not always the case. The probing tips need some amount of lateral compliance to compensate for the non-vertical positioning of the signal acquisition probe.